练习
1、It is necessary __f_o_r__us to learn to wait.
(of/for)
2、It was careless __o_f___me to break the cup .
（of/for)
3、It took them 1,000 yuan __to__b_u__y__this
It is easy __fo_r____ her to learn English well. It is clever ___o_f ____ you to solve the problem.
作主语
2、It takes sb. some time to do sth.
我每天花去三个小时完成家庭作业。 It takes me three hours to finish the homework every day. I spend three hours finishing the homework every day.
She can’t decide_w__hi_c_h_b_o_o_k__to__b_u_y__. =She can’t decide which book she should buy.
练习
1、Don’t forget _t_o_t_u_rn__o_ff_t_h_e_l_ig_h_t__.(关灯) 2、I happened _to__go__o_u_t _when he called me. （出去） 3、I don’t want__to__d_ep_e_n_d_o_n__o_th_e_r_s. (依赖别人） 4、Sam is learning__h_o_w__to__d_ri_v_e_a_c_a_r_. (怎样开车） 5、We promise _t_o_p_r_o_te_c_t__ the environment.(保护)
作主语
To hear your voice is so nice. It is so nice to hear your voice.
To study hard is very important. It is very important to study hard.
注意: 不定式作主语时，通常用it作形式主语，
被动： John _i_s_m__ad_e__to_ play the piano every day.
练习
1、Let him _f_in_i_s_h__ the work at once. (finish / to finish)
动词不定式
动词不定式的结构
肯定： to + V.原 或者 (to)+ V.原 否定：not/never + (to) + V.原
1) He likes to read novels. 2) I saw him come.hat house. 4) It is interesting to fly a kite. 5) Please let him not go there.
table. (buy)
4、It is my pleasure _t_o__c_a_r_r_y_ the box for you.
(carry)
练习
5、轮到我们打扫教室了。
It is our turn__to__c_l_e_a_n__th__e_c_l_a_s_s_r_o_o_m__. __
6、To waste time is to shorten life. （翻译成中文） 浪费时间就是缩短生命。
作主语
3、It is + n. (for sb) to do sth. It is my pleasure to help you with your English.
作主语
4、用在谚语中
To see is to believe. To say is easy, but to do is hard.
作宾语
1、动词+ to do sth.
常用动词有：
want / wish / like / would like / hope / plan / try / decide / learn / need / agree / begin / start / forget / remember / manage / seem / fail/ manage/ promise等
1、I hope to finish it tomorrow .
2、She plans to go and teach in the country.
作宾语
2、动词＋疑问词+to do
1、我不知道接下来该做什么。
I don’t know__w_h_a_t_to__d_o___ next.
2、她不能决定买哪本书。
作宾补-对宾语进行补充说明
1、动词 + 宾语（sb./sth.) + to do sth.
1、The teacher asked her to answer the question. 2、The doctor told me to have a good rest.
常用动词有：ask, tell, allow, want 等
把真正的主语放在后面。
1、It is +adj. for/ of sb. to do sth.
作主语
It +be + adj. +for/of sb. to do sth. for: adj. 多 为 描 述 不 定 式 行 为 的 特 征 （important/ necessary / interesting 等.） of: adj. 多为 描述主语的品质特征 （kind / nice / friendly / wise / foolish 等.）
2、动词+宾语+不带to的不定式 动词多为感官动词、使动词。
一感：feel 二听：hear, listen to 三使：make, let, have 四看：see, notice, watch, look at
John’s mother makes him play the piano every day.